Low-feedback compact wireless telephone

ABSTRACT

The present invention is directed to apparatus and methods for reducing sidetone feedback in a portable wireless telephone system by positioning the speaker and the microphone to reduce acoustic feedback and by controlling the amplifier gain in the transmitter section of the wireless telephone to reduce amplification of sidetone which has been acoustically coupled from the speaker to the microphone. The wireless telephone may be configured as a watch with a wrist strap for retaining it to the user, as a piece of jewelry such as a brooch or pendant, as a voice capable pager/intercom, or as an identification badge for an employee. In one embodiment, the base station includes circuitry for further reducing sidetone feedback. In additional embodiments, the wireless telephone may include a quick-release outboard battery, a retractable earpiece, and an ergonomic keypad.

FIELD OF THE INVENTION

The present invention relates to communications systems and inparticular to a compact implementation of a wireless telephone. Thepresent invention is also directed to a quick-release outboard battery,a retractable earpiece, and an ergonomic keypad which can be used withsuch a wireless telephone.

BACKGROUND OF THE INVENTION

As mobile communication has become increasingly critical to the conductof business, a need has arisen for smaller and more compact telephones.Until now the size and shape of the telephone has been driven in largepart by the size of the circuitry needed and by the need to maintain acertain separation between the telephone mouthpiece and the earpiece.Recent developments in integrated circuit technology have driven downthe size of the telephone circuitry. According to Olsen, U.S. Pat. No.4,847,818 issued Jul. 11, 1989 to Olsen and Blonder, U.S. Pat. No.5,239,521 issued Aug. 24, 1993, however, even if the telephone unit canbe sufficiently integrated to fit within a compact body, the telephonemicrophone and the telephone speaker must still be spaced a certainminimal distance apart in order to prevent feedback from the speakerthrough the microphone.

Feedback is inherent to telephone design. In the typical telephone, somefeedback of the microphone output back through the speaker (in the formof a sidetone) is necessary to serve as an indication to the user of howloudly he or she should speak. However, this feedback can cause problemsif it, in turn, is coupled back from the speaker through the microphone.The resulting feedback loop can lead to oscillations heard as an audiblehum or howl. Spatial separation reduces the amount of signal coupledfrom the speaker to the microphone and therefore prevents oscillation.

In compact telephones, such as a wrist-mounted telephone, the spatialseparation constraint forces the manufacturer to go through elaboratecontortions to place the microphone and/or speaker as satellitesattached to the telephone unit body. In Olsen, the speaker is placed atthe clasp of the watch while the microphone is either located at theopposite clasp or built into the body of the telephone unit. In Blonder,a special pivoting member is used to separate the microphone from thespeaker. Finally, in Yoshitake, U.S. Pat. No. 5,008,864 issued Apr. 16,1991, a speaking tube is used to provide directionality to the telephonemicrophone.

However, none of the above solutions is very practical. Olsen andYoshitake both require that the user remove the watch before placing orreceiving a telephone call. Blonder requires the addition of a separatelayer attached to the wrist strap that can pivot around the watch band.Such an approach drives up manufacturing costs and reduces reliability.

The feedback problem has also been addressed in the context of speakerphones. Speaker phones will howl if feedback of the sidetone from thespeaker through the microphone reaches too high a level. This problemcan be controlled by turning the speaker off during times when the useris speaking and by reducing the gain of the microphone amplifier duringperiods when the speaker is on. Another approach controls oscillation byreducing gain in the speaker amplifier during periods when the user isspeaking and then reducing gain in the microphone amplifier duringperiods when the user is quiet. Since both approaches rely on theaccurate detection of whether the user is speaking, they can causeaudible discontinuities in both the received and transmitted voicetransmissions at the start and end of user speech.

In addition to the feedback problem, portable radio telephones to date,especially those designed to be worn on the wrist, suffer from a numberof deficiencies. The power sources for portable radio telephones tend tobe short-lived and difficult to replace. Typically, the entire telephoneunit must be placed on a recharging stand, rendering it unavailable tothe user. Alternatively, the radio telephone must be shut-off to replacethe battery.

Also, when a user cannot use the speaker phone because of the need forprivacy, a separate earpiece must be located and carefully attached tothe phone unit. Separate earpieces are difficult to engage with thephone and easy to misplace.

Additionally, key pads on portable radio telephones, similar to otherminiaturized electronic devices such as calculator watches, typicallyare too small to be operated by hand. The user typically must utilize apen or other pointed object to activate a particular key.

It is clear that there is a need in the art for a compact wirelesstelephone which will minimize feedback while providing an acceptablevoice signal. In addition, there is a need in the art for a compactwireless telephone which includes an ergonomic keypad, a retractableearpiece attached to the wireless telephone and a power supply which iseasy to replace yet long-lasting.

SUMMARY OF THE INVENTION

The present invention is directed to a lowfeedback portable wirelesstelephone having a wireless transceiver connected to a microphone and aspeaker. The wireless telephone may either be configured as a watch witha wrist strap for retaining it to the user, as a piece of jewelry suchas a brooch or pendant, as a voice capable pager/intercom, or as anidentification badge for an employee.

In the embodiment where the radio telephone is used as an identificationbadge, each unit preferably is given a unique code which identifies theuser. The radio telephone operates as a transponder, sending anidentification signal at some predetermined interval or responding to asignal from a base station. By arranging several base stations around afacility, the present identification badge/portable radio telephone canoperate as a personnel locator and communicator.

The telephone includes a base station interface for transferringinformation between the telephone unit and a base station connected tothe local loop of a public telecommunications network. A directionalspeaker for radiating speaker sound in predominately a first directionis provided. A speaker circuit connected to the base station interfaceand the directional speaker is provided for driving the speaker with asignal received from the base station interface. A directionalmicrophone is positioned to be most sensitive to sound coming from asecond direction at approximately 90 degrees offset from the firstdirection. A microphone circuit connected to the directional microphoneand the base station interface is provided for driving the base stationinterface with a signal corresponding to sound received by thedirectional microphone. The microphone circuit includes an amplifierhaving an amplifier gain controlled to constrain the amount of speakersound fed back to the base station.

According to yet another aspect of the present invention, a base stationis described which works in conjunction with the above telephone toprovide a cordless or cellular telephone system.

According to yet another aspect of the present invention, a telephonesystem is described in which feedback is controlled in both the basestation and the telephone unit. The telephone includes a base stationinterface for transferring information between the telephone unit and abase station connected to the local loop of a public telecommunicationsnetwork. A directional speaker is provided for radiating speaker soundin predominately a first direction. A speaker circuit connected to thebase station interface and the directional speaker is provided fordriving the speaker with a signal received from the base stationinterface. A directional microphone is positioned to be most sensitiveto sound coming from a second direction at approximately 90 degreesoffset from the first direction. A microphone circuit is connected tothe directional microphone and the base station interface for drivingthe base station interface with a signal corresponding to sound receivedby the directional microphone. The base station includes a telephoneunit interface and a telephone line interface which includes means forreducing sidetone.

According to yet another aspect of the present invention, aquick-release outboard battery is described for use with a compactwireless telephone. A battery clasp is attached to the compact wirelesstelephone. The battery clasp has a battery attachment member andelectrical contacts connected to the telephone. A battery housingcontaining at least one battery is provided with a receiving member. Thereceiving member is arranged to engage with the attaching member on thebattery clasp so that the at least one battery electrically engages theelectrical contacts for powering the telephone.

In an embodiment in which the compact wireless telephone is designed tobe mounted on the wrist, the battery clasp may be located on the wriststraps or attached directly to the radio telephone.

The attaching member on the battery clasp is designed to allow quickrelease of the battery housing so that a replacement battery can beeasily attached to the compact wireless telephone. In the preferredembodiment, the attaching member is a T-shaped battery receivingstructure. The receiving member is a T-shaped receiving slot on thebattery assembly. In an alternate embodiment, the attaching member hasinwardly-biased opposing hook members, which create a compression forceon the battery housing to retain the battery housing to the batteryclasp.

In the preferred embodiment, the base station can be signalled tosuspend a call for a programmed period of time while a user changes thebattery.

The present invention is also directed to a retractable earpieceassembly for a compact wireless telephone in which an earpiececontaining a transducer is attached to the radio telephone by anelectrical cord. A rotatable cord spool is attached to the radiotelephone for storing the cord when it is in a retracted configuration.A retraction mechanism is provided for automatically rewinding the cordonto the spool after the cord has been manually withdrawn. In oneembodiment, the rotatable cord spool is retained in a housing attachedto the radio telephone or to wrist straps for the wrist phoneembodiment.

It will be understood that the compact wireless telephone may be used incombination with the quick release outboard battery and/or theretractable earpiece assembly discussed above.

The compact wireless telephone preferably includes an ergonomicallydesigned keypad in which the keys are canted so that they may beoperated by the user's finger rather than a pointed object.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top-level block diagram of a cordless telephone systemaccording to the present invention;

FIG. 2 is a front perspective view showing one embodiment of awrist-mounted wireless telephone having a battery assembly andretractable earpiece assembly attached thereto;

FIG. 3 is a rear perspective view of the wrist-mounted cordlesstelephone of FIG. 2;

FIG. 4 is a side view of one embodiment of the wrist-mounted cordlesstelephone of FIG. 2;

FIG. 5A is a block diagram of a base station;

FIG. 5B is a more detailed block diagram of sidetone cancellationcircuitry used in the base station of FIG. 5A according to the presentinvention;

FIG. 6 is a block diagram of the internal circuitry of the wrist-mountedcordless telephone of FIG. 2;

FIG. 7 is a perspective view of the preferred retractable earpieceassembly;

FIG. 7A is schematic illustration of the earpiece of FIG. 7;

FIG. 8 is an exploded view of the preferred compact wireless telephone;

FIG. 9 is an exploded view of an alternate outboard battery assembly;

FIG. 10 is a perspective view of an alternate battery clasp;

FIG. 11 is a perspective view of alternate outboard battery assembly;

FIG. 12 is a rear view of the alternate outboard battery assembly ofFIG. 11;

FIG. 13 is a bottom view of the alternate outboard battery assembly ofFIG. 11;

FIG. 14 is a side view of the alternate outboard battery assemblyattached to the alternate battery clasp;

FIG. 15 is a perspective view of an alternate outboard battery assembly;

FIG. 16 is a rear view of the alternate outboard battery assemblyattached to a battery clasp;

FIG. 17 is a bottom view of the alternate outboard battery assembly;

FIG. 18 is a side view of the alternate outboard battery assembly of thepresent invention;

FIG. 19 is a perspective view of the preferred battery clasp;

FIG. 20 is a rear plan view of a preferred battery assembly forengagement with the battery clasp of FIG. 19;

FIG. 21 is a perspective view of one preferred battery assembly engagedwith the preferred battery clasp as attached to the base plate of thephone;

FIG. 22 is a perspective view of the preferred battery clasp attached tothe base plate of the phone;

FIG. 23 is a perspective view of one embodiment of the preferred batteryassembly;

FIG. 24 is a bottom view of the battery assembly of FIG. 23;

FIG. 25 is a perspective view of an alternate embodiment of thepreferred battery assembly; and

FIG. 26 is a bottom view of the battery assembly of FIG. 25.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following detailed description of the preferred embodiment,reference is made to the accompanying drawings which form a part hereof,and in which is shown by way of illustration specific embodiments inwhich the inventions may be practiced. These embodiments are describedin sufficient detail to enable those skilled in the art to practice theinvention, and it is to be understood that other embodiments may beutilized and that structural changes may be made without departing fromthe spirit and scope of the present inventions. The following detaileddescription is, therefore, not to be taken in a limiting sense, and thescope of the present inventions is defined by the appended claims.

A top-level block diagram of a wireless telephone system 10 is shown inFIG. 1. In the system of FIG. 1, wireless telephone unit 12 is connectedthrough a base station 14 to the local loop 16 of a publictelecommunications network 18. Base station 14 includes an RF interfacefor communicating with wireless telephone unit 12 and telephone lineinterface circuitry which can be connected to local loop 16 in order tocommunicate over public telecommunications network 18 (see FIG. 5A). Thetelephone line interface circuitry may be a simple telephone lineconnection such as is used in the typical cordless telephone.

Alternatively, in systems 10 which support cellular communications, basestation 14 includes circuitry which communicates through a MobileTelecommunications Switching Office (MTSO)(not shown) to publictelecommunications network 18. In such systems, each base station 14 isassigned to a cell and the MTSO determines which cell is to communicatewith telephone unit 12. Base stations for use in cellular or cordlesstelephone applications are well known in the art and will not,therefore, be described in detail.

Wireless telephone unit 12 is designed to be easily carried by a user.In one embodiment, such as is shown in FIG. 2, unit 12 is configured asa wrist-mounted radio telephone 100 which can be attached to a user witha wrist band 132. In another embodiment, unit 12 may be worn as a pin orbrooch. In another embodiment, unit 12 may be suspended from a chainworn around the neck of a user, attached to clothing in a manner similarto an employee badge, or placed in a pocket.

FIG. 2 is a perspective view of the preferred embodiment of wirelesstelephone unit 12. In FIG. 2, compact wireless telephone 100 has akeypad 102, an LCD 104, and a speaker 106. The LCD 104 preferablydisplays the phone number dialed for an outgoing call or the sourcenumber for an incoming call, the date and time, indicates a low batterycondition, and whether the intercom or mute functions are activated (seeFIG. 6). A microphone 108 is provided on the front edge of the telephone100. The microphone 108 preferably is directionally offset from thespeaker 106 by 90 degrees.

Program keys 110 are provided on the side of the telephone 100 forprogramming the memory of the telephone (as will be discussed below).Volume keys 107 are provided on the opposite side of the radio telephone100 for adjusting the volume of the speaker 106 (see FIG. 4). The keypad102 includes the primary twelve keys on a standard telephone and threeadditional keys for a Talk function 112, a Hold function 116, and anIntercom function 114.

As discussed above, prior key pads on portable electronic devices aretypically so small that the user needs a pointed object such as a pen toactivate an individual key. The individual keys on the keypad 102preferably are canted or tilted so as to present a high point 103 whichfacilitates operation by a user's finger.

A retractable earpiece assembly 120 preferably is attached to the frontedge of the telephone 100 by a hinge mechanism 124. An outboard batteryassembly 130 is attached to the rear edge of the telephone 100 by asimilar hinge mechanism 126 (see FIG. 3). The wrist strap 132 isprovided for attaching the compact wireless telephone 100 to the wristof a user. However, it will be understood that the present compactwireless telephone 100, battery assembly 130, or earpiece 120 may beconfigured in any shape that is convenient for the user.

FIG. 3 is a rear perspective view of the compact wireless telephone 100showing an alternate outboard battery assembly 130. As will be discussedin detail below, a pair of rear hook members 134 engage withcorresponding slots (not shown) to releasably retain a battery housing136 to the phone 100.

The feedback loop formed by transmission of sidetone back from thereceiver to the transmitter is a critical problem in the design of acompact telephone or speaker phone. Sidetone is generated by the 2-wireto 4-wire hybrid circuit required by the telephone company and, to alesser extent, by reflections occurring within network 18 itself. Inaddition, many standard telephone integrated circuits have sidetonegeneration built in. All sources of sidetone are summed, amplified androuted through the user's speaker. This output must be loud enough tohear and, consequently, may be loud enough to be picked up and amplifiedby the telephone unit transmitter.

As noted above, spatial separation can be helpful in minimizing theamount of sidetone fed back through the transmitter. As components getsmaller, however, it is more and more difficult to achieve meaningfulseparation in a useful design. Therefore steps must be taken not only toisolate the transmitted and received sounds but also to reduce theamplification of sidetone reflected through the transmitter of telephoneunit 12.

One embodiment which reduces transmission of sidetone back through thetransmitter of telephone unit 12 is shown in FIGS. 2 and 4. FIG. 4 is aside view of a wireless telephone unit 100 which can be used in acellular or cordless telephone system 10. In the embodiments shown inFIGS. 2 and 4, spatial separation of the received and transmitted soundis enhanced by placing speaker 106 so that sound is radiated in adirection "d" which is a minimum of 90 degrees away from the directionin which microphone 108 is pointed.

In one such an embodiment, spatial separation is enhanced by using adirectional speaker and a directional microphone as speaker 106 andmicrophone 108. One such directional speaker is a Model No. KR2083speaker available from Keyrin of Taiwan. One such directional microphoneis a Model No. WM62-A microphone available from Matsushita of Tokyo,Japan. Further acoustic separation can be achieved by canting speaker106 such that the direction is greater than 90 degrees. In addition, ifspeaker 106 and microphone 108 are directional enough, angles of lessthan 90 degrees are possible.

Finally, as can be seen in FIG. 2, speaker 106 and microphone 108 areplaced as far away from each other as possible while still remaining inthe same package. By placing speaker 106 and microphone 108 so thattheir mounting axes are offset approximately 90 degrees or greater andby placing speaker 106 and microphone 108 on the diagonal at oppositecorners of telephone unit 100, acoustic coupling of speaker 106 tomicrophone 108 is minimized. The combination of directionality withpositioning results in an embodiment in which speaker 106 can be located2.5 cm (0.984 inches) from microphone 108. In the preferred embodiment,as is shown in FIGS. 2 and 4, the speaker 106 is located 3.5 cm (1.38inches) from the microphone 108.

The placement of speaker 106 and microphone 108 in a compact device suchas wireless telephone unit 12 can lead to some problems due to magneticcoupling of speaker magnets to oscillator inductors. Communicationsdevices such as telephone unit 12 typically include high Q tank circuitswhich are very sensitive to outside disturbances. The magnetic field andflux generated by the speaker magnet of speaker 106 can cause adisturbance in the oscillators which can feedback through speaker 106 toform another oscillatory loop. In one embodiment, oscillator inductorsare shielded and placed as far physically from speaker 106 as possible.For example, in the telephone unit 12 of FIG. 2 shielded oscillatorinductors are clustered in the vicinity of microphone 108 to reducemagnetic coupling between the inductors and speaker 106.

The interaction of the oscillator inductors with the speaker magnet canalso result in a microphonic effect seen when the speaker 106 magneticfield is moved suddenly with respect to the oscillator inductors. Suchan effect can be minimized by providing a secure, mechanically stableenvironment such that when telephone unit 12 is disturbed, both thespeaker magnet and the inductors move together. In one embodiment, asoft rubber bonnet or boot is placed around speaker 106 in order toprovide additional mechanical stability. In another embodiment, anannular ring is placed around speaker 106. In another embodiment, a softrubber cushion is built into the rubber keypad to provide the requiredmechanical support. It will be understood that a variety of techniquesand elastomeric materials are available for achieving mechanicalstability.

In addition to physical separation of speaker 106 and microphone 108 toreduce feedback of sidetone, steps have been taken to reduce sidetone.For instance, the frequency of oscillation of sidetone feedback tends tobe centered about a particular frequency. Therefore, the effects ofsidetone on telephone unit 12 can be minimized by either providing anotch filter at that frequency in the circuit driving speaker 106 or byreducing feedback of the sidetone at that frequency in the 2-wire to4-wire hybrid circuit. One method of reducing feedback of the sidetonewithin the 2-wire to 4-wire hybrid circuit is shown in FIGS. 5A and 5B.

In FIG. 5A, base station 14 includes a polarity and overvoltageprotection circuit 80, a loop holding circuit 82, a 2-wire to 4-wirehybrid circuit 84, a wireless telephone interface 86, a ring detectcircuit 88 and a controller 90. Polarity and overvoltage protectioncircuit 80 is of the type typically used in electronic telephones. Loopholding circuit 82 draws the off-hook current required to tell localloop 16 that base station 14 wishes to be connected to publictelecommunications network 18. 2-wire to 4-wire hybrid circuit 84provides the signal separation and rejoining required by the telephonecompany. Wireless telephone interface 86 communicates with telephoneunit 12 through any known means of wireless communication (radio,infrared, ultrasonic, etc.). Controller 90 controls the interface withlocal loop 16 and communication over wireless telephone interface 86Ring detect circuit 88 detects the ring signal received from local loop16 and generates an interrupt to controller 90 regarding the detectionof the ring signal.

One embodiment of a 2-wire to 4-wire hybrid circuit 84 is shown in FIG.5B. In circuit 84 of FIG. 5B, a transformer 91 isolates base station 14from local loop 16. Transformer 91 includes windings 92 and 93. Winding92 is connected to the local loop side of hybrid circuit 84 whilewinding 93 is connected to the telephone side of circuit 84. Winding 93has three taps 94.1-3. Taps 94.1 and 94.2 are electrically connected toa receiver amplifier circuit 95 in a manner known in the art while tap93.3 is electrically connected to transmitter amplifier circuit 97.Audio received at transformer 91 from local loop 16 is out of phase andis therefore differentially summed by amplifier 96 of receiver amplifiercircuit 95. Meanwhile, an audio signal obtained from transmitteramplifier circuit 97 is in phase and therefore cancelled. In oneembodiment, cancellation is frequency dependent. That is, a notch filteris used to attenuate frequencies centered around those frequenciesassociated with sidetone oscillations. In practice the frequency ofsidetone oscillation varies according to the construction of hand unit10 and the placement of speaker 106 and microphone 108. Therefore, thecircuit must be tuned to compensate. In one such embodiment, amplifiers96 and 98 are Model No. LM324 operational amplifiers such as areavailable from Motorola. In such an embodiment, an advantageous choiceof impedances Z1-Z12 is as follows:

    ______________________________________                                        Z1             0.1 μF                                                      Z2             0.1 μF in series with 100 kΩ                          Z3             2 MΩ                                                     Z4             100 kΩ                                                   Z5             100 kΩ                                                   Z6             10 kΩ                                                    Z7             100 kΩ                                                   Z8             680 Ω                                                    Z9             0.1 μF                                                      Z10            330 Ω                                                    Z11            6.8 kΩ                                                   Z12            100 kΩ                                                   ______________________________________                                    

Feedback of sidetone can also be controlled by judicious selection oftransmitter amplifier gains. Transmitter amplifier gains may be set sothat sidetones received by microphone 108 are not amplified above athreshold level. One embodiment of a low feedback wireless telephoneunit 12 is shown in FIG. 6. In telephone unit 12 of FIG. 6, telephoneunit 12 includes a controller 38, a base station interface circuit 40for transferring information between base station 14 and telephone unit12, a speaker circuit 42, a directional speaker 44, a microphone circuit46 and a directional microphone 48. Speaker circuit 42 is connected tobase station interface circuit 40 and directional speaker 44 and is usedfor driving directional speaker 44 with a speaker signal received frombase station 14. Microphone circuit 46 is connected to directionalmicrophone 48 and base station interface circuit 40 and is used fordriving base station interface circuit 40 with a microphone signalcorresponding to sound, including speaker sound, received by directionalmicrophone 48.

In the embodiment shown in FIG. 6, speaker circuit 42 includes an AFamplifier 52, a high pass filter 54, an expander 56, deemphasis 58,optional descrambler 59, band pass filter 60, optional mute gate 62 andoutput amplifier 64. In one such embodiment, speaker circuit 42 isdesigned to provide approximately 29.6 dB of gain at 1 kHz.

Microphone circuit 46 is designed to have an amplifier gain controlledto limit the amount of speaker sound fed back to the base station. Inthe embodiment of FIG. 6, microphone circuit 46 includes a preamplifier66, a bandpass filter 68, optional scrambler/bandpass filter 70,preemphasis 72, compressor 74, mute gate 76 and summing amplifier 78. Inone such embodiment, preamplifier 66 has a gain of 20 dB,scrambler/bandpass filter 70 has unity gain, preemphasis 72 adds 6dB/octave of preemphasis and summing amplifier 78 has unity gain. Inaddition, the transmitter amplifier of base station interface 40 is partof the Motorola MC2833 transmitter integrated circuit, which adds 9.5 dBof gain.

In one embodiment, antenna 79 of base station interface 40 is a dipoleantenna embedded in the wrist strap of wireless telephone unit 12. In analternate embodiment, antenna 79 is a loop antenna embedded in or as anintegral part of cover plate 150 of wireless telephone unit 100 (such asis shown in FIG. 8).

FIGS. 7 is a perspective view of the preferred retractable earpieceassembly 120. FIG. 7A is a schematic illustration of the retractableearpiece assembly 120 having an earpiece 140 containing a transducer 141attached to the earpiece housing 122 by a cord 144. The cord 144preferably is braided to provide increase strength and greaterreliability. The cord 144 is engaged with a rotatable cord spool 146. Aretraction mechanism 148, such as a coiled leaf spring, automaticallyrewinds the cord 144 onto the spool 146 after the cord has been manuallywithdrawn. A switch 142 is provided to activate the transducer 141 whenthe earpiece 140 is withdrawn a predetermined distance from the earpiecehousing 122 and deactivate the transducer 141 when the earpiece 140 isretracted. A hinge mechanism 147 is provided for attaching the wriststrap 132 to the earpiece assembly 120. A retraction mechanism known tobe suitable for this purpose is disclosed in U.S. Pat. No. 3,984,645issued to Kresch on Oct. 5, 1976, which is hereby incorporated byreference.

FIG. 8 is an exploded view of the preferred compact wireless telephone100. Cover plate 150 has keypad openings 152 for the keypad 102. Aspeaker opening 154 is provided in the uppermost corner of the coverplate 150 so as to be as far from the microphone opening 158 aspossible. A midplane 156 is provided to support the keypad 102. A cutout158 is provided in the midplane 156 for the speaker 106. An LCD 104 isinterposed between the midplane 156 and the printed circuit board 160 sothat the LCD 104 is visible through the openings 162, 164 in themidplane 156 and cover plate 150, respectively. A back plate 166 isprovided with numerous removable supports 168 to support the PC board160 and other components. The removable supports 168 may be snapped offduring assembly to make room for electrical components as required.Finally, the back plate 166 has portions of a hinge mechanism 124, 126for attaching the radio telephone 100 to a user.

The back plate 166 may also include a non-audible tactile annunciator184 to alert the user that a page or call is being received. Althoughthe annunciator 184 is preferably a micro-motor with an eccentric cam,it will be understood that a variety of vibro-tactile mechanisms aresuitable for this purpose, such as a piezo-electric device, and that thepresent invention is not limited by the particular mechanism disclosed.

When assembled, the present compact wireless telephone 100 is only 0.275inches (7.0 mm) thick. The preferred phone 100 is 1.57 inches (39.9 mm)in the direction "W" and 2.17 inches (55.1 mm) in the direction "L" sothat it does not extend out orthogonally from the user's wrist. Thepreferred wrist mounted compact wireless phone embodiment can thereforeeasily be worn even by individuals with small wrists.

FIG. 19 is a perspective view of a preferred battery clasp 300 having a"hot shoe" battery receiving structure 302. The battery receivingstructure 302 is generally "T" shaped, with a top portion 304 which iswider than a bottom portion 306. The top portion 304 has a pair ofdetents 308 on each edge for retaining a battery assembly (see FIG. 21)to the clasp 300. In the preferred embodiment, the detents 308 alsooperate as electrical contact points.

The edges 310 of the top portion 304 form rails for engaging with acorresponding "T" shaped opening 312 in a battery assembly 314 (see FIG.20). The battery assembly 314 preferably has spring-loaded electricalcontacts 316 for releasably engaging with the detents 308. Thespring-loaded contacts 316 allow the battery assembly 314 to be slid onand off of the battery receiving structure 302. The electrical contacts316 preferably have a flexing portions (not shown) similar to thosedisclosed in FIG. 9 which extend past the hinge 320 to the phone 100(see also FIGS. 2 and 3). However, it will be understood that a varietyof techniques may be used to electrically connect the battery assembly314 with the phone 100, such as, for example, a shielded wire.

The process of exchanging a battery, known as lock-and-load, allows theuser to quickly substitute a fresh battery as needed without terminatinga call in progress. The user presses the Hold key 116 to signal to thebase station 14 to suspend the call. The RF interface is terminated andthe base station 14 holds the call for a programmed period of time.During this Hold period, the user may change batteries. With the batteryreplaced, the user reestablishes communication with the base station 14by again pressing the Hold key 116. The RF link is reestablished and thecall reconnected to the line. The PC board 160 preferably contains aseries of capacitors which provide power to the control circuit tomaintain the time of day while the user changes the battery assembly130.

The clasp 300 has a hinge 320 for engagement with a corresponding hingeon 124 on the back plate 166 (see FIGS. 21 and 22). Additionally, ahinge 322 is provided on the opposite side of the clasp 300 forengagement with a wrist strap (not shown). Although the clasp 300 isgenerally configured for use with a wrist mounted phone, it will beunderstood that the present quick-release clasp 300 may be used withother configurations of the phone 100.

FIGS. 22 illustrates the clasp 300 attached to the back plate 166. FIG.21 illustrates one embodiment of the battery assembly 314 engaged withthe clasp 300 of FIG. 22.

FIG. 23 is a perspective view of one embodiment of the preferred batteryassembly 314 having a primary portion 326 and a secondary portion 328.The secondary portion 328 is preferably shaped to follow the contour ofa users wrist (see FIG. 21). FIG. 24 is a bottom view of the batteryassembly 314 showing the "T" shaped opening 312 for engagement with thebattery receiving structure 302. The opening 312 is preferably wider atthe entrance 324 to facilitate engagement with the battery receivingstructure 312. The battery assembly 314 preferably has three batterycompartments 330.

FIG. 25 is a perspective view of an alternate preferred battery assembly314' for engagement with the clasp 300. FIG. 26 is a bottom view of thebattery assembly 314' showing the "T" shaped opening 312 for engagementwith the battery receiving structure 302. The battery assembly 314' isdesigned to hold up to four batteries in the compartments 330'.

FIG. 9 is an exploded view of an alternate outboard battery assembly130. Battery clasp 170 has a hinge 126' for connecting with the hinge126 on the base plate 166. A second hinge 172 is provided for connectingto the wrist strap 132 (see FIG. 2). A pair of electrical contacts 174,176 are attached to the battery clasp 170 by an electrical contactretaining member 178. The electrical contacts 174, 176 have a flexportions 180 which connects to a flex circuit (not shown) in the radiotelephone 100. The flex portions 180 allows the battery assembly 130 torotate on the hinge mechanism 126, 126' while maintaining a connectionwith the phone 100.

FIG. 9 illustrates an outboard battery assembly 130 with three batteries182 contained in the housing 136. The batteries 182 preferably arecommon nickel metal hydride batteries which are low cost and readilyavailable. However, it will be understood that a variety of batteriesand battery configurations are possible and that the present inventionis not limited in any way by the specific number or type of batteries182 contained in the outboard battery assembly 130.

FIG. 10 is a perspective view of the battery clasp 170 with a batteryreceiving surface 193. A pair of rear hook members 190 having bodyportions 192 and rear hook portions 194 are provided proximate the hinge126'. Opposing front hook member 196 with a front hook portion 198 isprovided proximate the hinge 172.

FIG. 11 is a perspective view of the outboard battery assembly 130illustrating a front receiving slot 200 in the battery housing 136. FIG.12 is a rear view of the outboard battery assembly 130 showing rearreceiving slots 202 in the housing 136. FIG. 13 is a bottom view of thebattery housing 136 showing battery compartments 204 for retaining thebatteries 182. A pair of dividers 206, 208 preferably are providedinside the battery housing 136 to maintain a separation between thebatteries 182 and to orient the batteries 182 with respect to theelectrical contacts 174, 176.

FIG. 14 is a side view of the alternate outboard battery assembly 130engaged with the battery clasp 170. The front hook portion 198 and rearhook portions 190 preferably are biased inward towards the batteryhousing 136 so that they engage with the front receiving slot 200 andthe rear receiving slots 202 (see FIG. 13). The battery clasp 170preferably is constructed of a lightweight constructed material such asmetal or plastic, which allows the front hook member 196 and rear hookmembers 190 to create a compressive retaining force on the batteryhousing 136.

To remove the outboard battery assembly 130 from the battery clasp 170,the user merely slides the battery housing 136 along the batteryreceiving surface 193 toward the front hook portion 198 of the fronthook member 196. This movement releases the battery housing 136 from therear hook portions 190, allowing the outboard battery assembly 130 to betipped and removed from the battery clasp 170. Installation of a freshbattery assembly 130 is performed by reversing the above procedure. Acall may be retained by the base station 14 as discussed above.

FIG. 15 is a perspective view of an alternate outboard battery assembly210 in which the battery housing 212 has a primary portion 214 and asecondary portion 216. The secondary portion 216 provides additionalspace for holding battery elements (not shown). FIG. 16 is a rear viewof the alternate outboard battery assembly 210 having a pair of rearreceiving slots 230 for engaging with the rear hook members 224 on thebattery clasp 220. FIG. 17 is a bottom view of the battery housing 212showing a front hook engaging member 232 for engaging with the fronthook 222 (see FIG. 18). The front hook engaging means 232 may alsooperate as a divider between the battery compartments 204' forseparating and orienting the batteries (not shown).

FIG. 18 is a side view of the alternate outboard battery assembly 210engaged with a battery clasp 220. The battery clasp 220 has a fronthinge 126" for engaging with the compact wireless telephone 100 and arear hinge 172 double prime for engaging with a wrist strap (not shown).The secondary portion 216 of the battery housing 212 is designed togenerally follow the contour of the human wrist along the wrist strap(not shown). The battery clasp 220 has a front hook 222 and a pair ofrear hooks 224 which are biased to create a compression force on thehousing 212 so as to retain the alternate outboard battery assembly 210to the clasp 220. The alternate battery assembly 210 is installed andremoved in a similar manner to the battery assembly 130.

It is to be understood that the above description is intended to beillustrative, and not restrictive. Many other embodiments will beapparent to those of skill in the art upon reviewing the abovedescription. Although the above inventions have been described inconnection with a cordless telephone system, it should be apparent thatthe concepts extend to any cordless or cellular telephone applicationrequiring a compact, portable telephone or speaker phone unit. The scopeof the invention should, therefore, be determined with reference to theappended claims, along with the full scope of equivalents to which suchclaims are entitled.

What is claimed is:
 1. A wireless telephone for communicating with abase station, the wireless telephone comprising:a telephone body membercontaining a base station interface including a radio transmitter andreceiver for transferring information between the base station and thewireless telephone; a directional speaker having a speaker mountingaxis, the directional speaker mounted with respect to the body memberand such that the directional speaker radiates speaker sound inpredominately a first direction along the speaker mounting axis; aspeaker circuit contained within the telephone body member, the speakercircuit connected to the base station interface and the directionalspeaker for driving the directional speaker with a speaker signalreceived from the base station; a directional microphone that has amicrophone mounting axis substantially corresponding to a direction ofgreatest sensitivity, wherein the directional microphone is mounted withrespect to the body member such that the microphone mounting axis isapproximately 90 degrees or greater away from the speaker mounting axisand Further wherein the directional microphone is located betweenapproximately 2.5 cm and 6.8 cm from the directional speaker along atleast one surface of the body member; and a microphone circuit containedwithin the telephone body member, the microphone circuit connected tothe directional microphone and the base station interface for drivingthe base station interface with a microphone signal corresponding tosound received by the directional microphone.
 2. The telephone of claim1 wherein the directional microphone is located between approximately2.5 cm and 3.5 cm from the directional speaker along at least onesurface of the body member.
 3. The telephone of claim 1 wherein the bodymember is a single body element having at least two surface positionssuch that the directional microphone and directional speaker can bemounted with their respective mounting axes separated by approximately90 degrees.
 4. The telephone of claim 3 wherein the body member has atleast two connected faces, one face being positioned at an angle ofapproximately 90 degrees with respect to the other face, the speakermounting axis being substantially perpendicular relative to one of thetwo faces and the microphone mounting axis being substantiallyperpendicular to the other of the two faces.
 5. The telephone of claim 3wherein the single body element has a top face and a side face, the sideface being positioned at an angle of approximately 90 degrees withrespect to the top face, the speaker mounting axis being substantiallyperpendicular relative to the top face and the microphone mounting axisbeing substantially perpendicular to the side face.
 6. The telephone ofclaim 5 wherein the speaker and microphone are positioned such that thespeaker mounting axis and the microphone mounting axis are in anonintersecting relationship and separated by an offset distance.
 7. Thetelephone of claim 6 wherein the offset distance is approximately anentire length of the top face.
 8. The telephone of claim 6, wherein thespeaker and microphone are separated by approximately a diagonaldistance across the top face of the single body element.
 9. Thetelephone of claim 1 wherein the speaker and microphone are positionedsuch that the speaker mounting axis and the microphone mounting axis arein a nonintersecting relationship and separated by an offset distance.10. The telephone of claim 1 wherein the microphone circuit has areduced gain which limits the amount of speaker sound fed back to thebase station.